Gate driver circuits are pervasive in many electronic applications from computers to automobiles to solar power generation. A gate driver circuit may be used to implement a portion of a switched-mode circuit, including, for example, a switched-mode power supply or another switched-mode circuit. Switched-mode circuits may be implemented using a gate driver circuit to drive the gates of one or more switch transistors, such as IGBT or MOSFET power devices.
In some cases, a negative voltage supply for a gate driver circuit may become floating or undefined due to a physical defect such as bond wire lift, bond wire breakage, solder joint lift, or due to another factor such as a failure of the external power supply or other circuit. In an event such as this, a parasitic diode between the negative voltage supply and another voltage reference may be forward-biased and produce a high current path. For example, the negative voltage supply may be a VEE supply, and the voltage reference may be a GND connected to the emitter or source of the driven switch transistor. In some cases, a gate driver circuit may have an Under-Voltage Lockout (UVLO) circuit that compares the VEE voltage with the GND voltage and deactivates the circuit when VEE is within some defined voltage of GND. However, in some cases it may be desired that some or all of the circuit continue to operate even when VEE is close to or equals GND, in which case an UVLO circuit is unsuitable. Moreover, in some embodiments using a gate driver circuit, VEE is connected to GND, and thus it is not possible to use an UVLO circuit that compares VEE and GND. For example, VEE and GND may be connected in some gate driver circuits that use an active Miller clamp to prevent re-turn-on of the switch transistor. Some gate driver circuits may include protection circuitry that senses the onset of a high current condition and takes preventative action to avoid or reduce the high current.